compared to the control day. The IR group did not respond to the same treatment except for a Ž
. slight increase in drinking behaviour 9.6 vs. 6.5; p - 0.05 at the age of 8 weeks. No differences
were observed in the frequency or length of lying bouts, nor health or production parameters between the three groups.
It is concluded that a predictable feeding schedule may not be very important for milk-fed dairy calves. However, when the calves are customised to predictable feeding times, occasional
deviations from that schedule may cause frustration when their expectations are not fulfilled. q
2000 Elsevier Science B.V. All rights reserved.
Keywords: Cattle; Feeding; Nutrition; Feeding-times; Predictability; Circadian rhythm
1. Introduction
Predictability of management routines such as milking, feeding or inspection of the animals has not received much attention in the study of the impact of management on
animal behaviour and welfare. The present experiment was conducted to assess the impact of predictability of feeding on animal welfare.
It has been found that many physiological processes and behaviours follow circadian Ž
rhythms, primarily controlled by day length see reviews by Mrosovsky et al., 1989; .
Mistlberger, 1994 . However, some anticipatory processes and activities can additionally Ž
be altered by manipulating the feeding schedule of animals Boulos and Terman, 1980; .
Honma et al., 1983; Rosenwasser et al., 1983 . This indicates that there are at least two systems capable of controlling rhythmic biological processes. One is driven by a
pacemaker, adjusted by day length but unaffected by other external stimuli such as Ž
feeding times but the other system is dependent upon external stimuli Honma et al., .
1983; Mrosovsky et al.,1989; Rosenwasser et al., 1983 . Under normal light–dark conditions, the two systems are usually coupled to each other but if a stable feeding
schedule has been entrained, the anticipatory activity system will free-run, even if the Ž
animal is held in stable light or dark conditions Boulos et al., 1980; Aschoff et al., .
1983; Mistlberger, 1994 . This means that animals can learn to anticipate regular feeding times, even if they are held in environments with either no, or irregular diurnal
variations in light intensity. Various experiments have related the loss of predictability or controllability to the
Ž .
development of experimental neurosis in animals Mineka and Kihlstrom, 1978 . A Ž
. classical example of experimental neurosis in dogs was described by Pavlow 1960 , but
also in more natural and less radical experiments, researchers have reached similar Ž
. conclusions Glass and Singer, 1972; Andrews and Rosenblum, 1991 .
Other studies have shown that predictable events can cause more stress to the animals Ž
. than unpredictable events Jordan et al., 1984; Bloomsmith and Lambeth, 1995 . Infant
squirrel monkeys, removed from their mothers showed less stress responses if the Ž
. duration of the removal was unpredictable than predictable Jordan et al., 1984 . It has
also been demonstrated that chimpanzees kept on an unpredictable feeding schedule show more ‘‘species-appropriate behaviour’’ than those on a predictable schedule
Ž .
Bloomsmith and Lambeth, 1995 . Furthermore, behaviour often referred to as welfare Ž
. reducing stereotypies, agonistic behaviour is seen prior to feeding times in many
Ž .
species Wasserman and Cruikshank, 1983; Mason, 1993 .
Therefore, it is unclear to which extent variable management routines on farms affect the welfare of the animals, and whether the effect on welfare is positive or negative. The
Ž . present study addresses two questions: 1 does an unpredictable feeding schedule affect
Ž . the behaviour, production or health of dairy calves and 2 do animals that are used to a
predictable feeding schedule react otherwise to occasional deviations in this schedule, than animals that are fed according to an unpredictable schedule.
2. Materials and methods
